Horizons: Exploring the Universe (MindTap Course List)
14th Edition
ISBN: 9781305960961
Author: Michael A. Seeds, Dana Backman
Publisher: Cengage Learning
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Chapter 12, Problem 11P
To determine
The wavelength of infrared
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If the hottest star in the Carina Nebula has a surface temperature of 51,000 K, at what wavelength (in nm) does it radiate the most energy?
Hint: Use Wien's law:
?max =
2.90 ✕ 106 nm · K
T
How does that compare with 91.2 nm, the wavelength of photons with just enough energy to ionize hydrogen?
-The wavelength calculated above is shorter than 91.2 nm. Photons at this calculated wavelength will have more than enough energy to ionize hydrogen.
-The wavelength calculated above is longer than 91.2 nm. Photons at this calculated wavelength will have more than enough energy to ionize hydrogen.
-The wavelength calculated above is shorter than 91.2 nm. Photons at this calculated wavelength will not have enough energy to ionize hydrogen.
-The wavelength calculated above is longer than 91.2 nm. Photons at this calculated wavelength will not have enough energy to ionize hydrogen.
A galaxy's rotation curve is a measure of the orbital speed of stars as a function of distance
from the galaxy's centre. The fact that rotation curves are primarily flat at large galactocen-
tric distances (vrot(r) ~ constant) is the most common example of why astronomer's believe
dark matter exists. Let's work out why!
Assuming that each star in a given galaxy has a circular orbit, we know that the accelera-
tion due to gravity felt by each star is due to the mass enclosed within its orbital radius r and
equal to v?/r. Here, ve is the circular orbit velocity of the star. (a) Show that the expected
relationship between ve and r due to the stellar halo (p(r) xr-3.5) does not produce a flat
rotation curve. (b) Show that a p(r) ∞ r¯² density profile successfully produces a flat ro-
tation curve and must therefore be the general profile that dark matter follows in our galaxy.
The figure below shows the spectra of two galaxies A and B.
Chapter 12 Solutions
Horizons: Exploring the Universe (MindTap Course List)
Ch. 12 - Why is it difficult to specify the dimensions of...Ch. 12 - Why didn’t astronomers before Shapley realize how...Ch. 12 - Prob. 3RQCh. 12 - Prob. 4RQCh. 12 - Prob. 5RQCh. 12 - Prob. 6RQCh. 12 - Prob. 7RQCh. 12 - Prob. 8RQCh. 12 - Prob. 9RQCh. 12 - Prob. 10RQ
Ch. 12 - Prob. 11RQCh. 12 - Prob. 12RQCh. 12 - Prob. 13RQCh. 12 - Prob. 14RQCh. 12 - Prob. 15RQCh. 12 - Prob. 16RQCh. 12 - Prob. 1DQCh. 12 - Prob. 2DQCh. 12 - Prob. 1PCh. 12 - Prob. 2PCh. 12 - Prob. 3PCh. 12 - Prob. 4PCh. 12 - Prob. 5PCh. 12 - Prob. 6PCh. 12 - Prob. 7PCh. 12 - If the Sun is 4.6 billion years old, how many...Ch. 12 - Prob. 9PCh. 12 - Prob. 10PCh. 12 - Prob. 11PCh. 12 - Prob. 12PCh. 12 - Prob. 1LTLCh. 12 - Prob. 2LTL
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- A given star orbits the center of its galaxy at an average speed of v_star, at a distance of r_star from the center. The galaxy has 2 spiral arms, and the arms themselves orbit slower than the star -- at the same radius, they orbit at a speed of v_arm (in the same direction as the star). The galaxy's age is t_gal. In the history of this galaxy, how many times did this star cross through a spiral arm? Values: v_star = 200 km/s, r_star = 9 kpc, v_arms = 46 km/s, t_gal = 4 Gyrarrow_forwardThe disk of the Milky Way galaxy contains roughly 200 billion (1 billion = 109 ) stars. The disk is not solid, but rather is a volume about 100,000 light-years in diameter (1 ly = 9500 billion kilometers) and 1000 light-years in thickness. What is the number density of stars in the Milky Way galaxy disk, in units of stars per cubic light-year? How about in units of stars per cubic km?arrow_forwardThe difference in absolute magnitude between two objects is related to their fluxes by the flux-magnitude relation: FA / FB = 2.51(MB - MA) A distant galaxy contains a supernova with an absolute magnitude of -19. If this supernova were placed next to our Sun (M = +4.8) and you observed both of them from the same distance, how much more flux would the supernova emit than the Sun? Fsupernova / FSun = ?arrow_forward
- Suppose you want to observe the molecular gas in a galaxy with redshift z using the rotational transition of CO J=4-3. What frequency would you observe this transition at? (Hint: the CO J=1-0 emits a photon at 115.27 GHz, and higher order transitions emit photons with frequencies in multiples of J. Express your answer as an integer. Values: z = 3.7arrow_forwardIf the active core of a galaxy contains a black hole of 106?Θ (1 million solar masses), what will the orbital velocity be for matter orbiting the black hole at a distance of 0.33 AU? (Hint: use the formula for orbital velocity: ?=√???; where ?=6.67×10−11 ?3?? ?2 and ?Θ= 2.0×1030 ??. Note: 1 ??=1.50×1011 ?)arrow_forwardI answer is not 100, I also tried 21. I need help! Thank you!arrow_forward
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